A Novel Inclusion Complex of 8-Hydroxyquinoline Sandwiched Between Two β-Cyclodextrins

A supramolecular inclusion complex was prepared between beta-cyclodextrin (beta-CD) and 8-hydroxyquinoline, and its crystal structure was investigated by single-crystal X-ray crystallography. The asymmetric unit consists of two beta-CDs, one 8-hydroxyquinoline, two ethanol and thirty water molecules. Two beta-CDs form a head-to-head dimer by means of extensive hydrogen bonding across the secondary hydroxyl groups. One 8-hydroxyquinoline molecule is sandwiched in the interface of the dimer and is parallel to the plane of beta-CD macrocycle. Each beta-CD of the dimer includes one ethanol molecule in its cavity. Thirty water molecules are distributed in the interstices between beta-CD dimers. The results indicate that the interface of the beta-CD dimer has stronger inclusion ability than the cavity of beta-CD for some suitable planar molecules. The novel inclusion structure results from the competitive inclusion of 8-hydroxyquinoline and ethanol molecules.